Quality and rate control strategy for digital audio
First Claim
1. A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method of controlling quality of information in a constant bitrate encoder, wherein the encoder outputs the information at variable quality and compressed to a constant or relatively constant bitrate, the method comprising:
- quantizing a block of information to meet constant or relatively constant bitrate requirements, wherein the encoder adjusts quantization step size of the quantizing in view of a target quality parameter for the block, thereby reducing number of changes in quality and smoothing transitions between the changes in quality; and
entropy coding the quantized block of information.
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Accused Products
Abstract
An audio encoder regulates quality and bitrate with a control strategy. The strategy includes several features. First, an encoder regulates quantization using quality, minimum bit count, and maximum bit count parameters. Second, an encoder regulates quantization using a noise measure that indicates reliability of a complexity measure. Third, an encoder normalizes a control parameter value according to block size for a variable-size block. Fourth, an encoder uses a bit-count control loop de-linked from a quality control loop. Fifth, an encoder addresses non-monotonicity of quality measurement as a function of quantization level when selecting a quantization level. Sixth, an encoder uses particular interpolation rules to find a quantization level in a quality or bit-count control loop. Seventh, an encoder filters a control parameter value to smooth quality. Eighth, an encoder corrects model bias by adjusting a control parameter value in view of current buffer fullness.
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Citations
100 Claims
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1. A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method of controlling quality of information in a constant bitrate encoder, wherein the encoder outputs the information at variable quality and compressed to a constant or relatively constant bitrate, the method comprising:
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quantizing a block of information to meet constant or relatively constant bitrate requirements, wherein the encoder adjusts quantization step size of the quantizing in view of a target quality parameter for the block, thereby reducing number of changes in quality and smoothing transitions between the changes in quality; and
entropy coding the quantized block of information. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. In an audio encoder, a computer-implemented method comprising:
compressing a block of frequency coefficients, wherein the compressing includes, quantizing the block of frequency coefficients;
comparing a quality measure for the block to a quality target;
comparing a bit-count measure for the block to a minimum-bits target and to a maximum-bits target. - View Dependent Claims (11, 12, 13)
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14. A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method of controlling quality and bitrate in an audio encoder, the method comprising:
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determining one or more target quality parameters, a first target quality parameter of the one or more target quality parameters indicating an acceptable audio quality;
determining plural target bitrate parameters, a first target bitrate parameter of the plural target bitrate parameters indicating a minimum acceptable number of bits produced, and a second target bitrate parameter of the plural target bitrate parameters indicating a maximum acceptable number of bits produced;
compressing audio information, wherein quantization of the audio information is based at least in part upon the first target quality parameter, the first target bitrate parameter, and the second target bitrate parameter. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. In an audio encoder, a computer-implemented method comprising:
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computing a value of a control parameter for a block of spectral audio information, wherein the control parameter is based at least in part upon one or more complexity estimate noise measures; and
quantizing the block, wherein the value of the control parameter at least in part regulates the quantizing. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
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35. An audio encoder comprising:
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means for computing a value of a control parameter for audio information, wherein the control parameter is based at least in part upon one or more reliability measures for complexity estimates; and
a quantizer for quantizing the audio information, wherein the value of the control parameter at least in part regulates the quantizer. - View Dependent Claims (36, 37, 38, 39)
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40. A computer-readable medium having encoded therein computer-executable instructions for causing a computer programmed thereby to perform a method of regulating output of an audio encoder, the audio encoder processing plural blocks of audio information, wherein each of the plural blocks has one of plural available block sizes, the method comprising:
for each of the plural blocks of audio information, computing one or more values of control parameters, wherein the computing includes normalizing block size for the block; and
quantizing the block, wherein the one or more values of control parameters at least in part regulate the quantizing. - View Dependent Claims (41, 42, 43, 44)
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45. An audio encoder comprising:
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a frequency transformer for transforming a time domain block of audio samples into a transform block of frequency coefficients, wherein the transform block has a transform block size selected from among plural available transform block sizes;
means for computing a value of a control parameter, wherein the computing includes normalizing transform block size for the transform block; and
a quantizer for quantizing the transform block, wherein the value of the control parameter at least in part regulates the quantizing. - View Dependent Claims (46, 47, 48, 49, 50)
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51. A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method comprising:
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adjusting quantization of a block of frequency coefficients for audio information in a quality control quantization loop until satisfaction of one or more quality criteria; and
following and outside the quality control quantization loop, adjusting the quantization of the block in a bitrate control quantization loop until satisfaction of one or more bitrate criteria. - View Dependent Claims (52, 53, 54, 55)
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56. In an audio encoder, a computer-implemented method of controlling bitrate and audio quality, the method comprising:
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in each of one or more iterations of a first quantization loop, quantizing audio information;
measuring audio quality;
comparing the measured audio quality to one or more target quality parameters;
in each of one or more iterations of a second quantization loop following and outside of the first quantization loop, measuring bit count of the audio information; and
comparing the measured bit count to one or more target bit count parameters. - View Dependent Claims (57, 58, 59, 60, 61, 62, 63, 64)
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65. A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method comprising:
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selecting a quantization level within a range of quantization levels, wherein the selecting accounts for non-monotonicity of quality measure as a function of quantization level within the range; and
quantizing audio information by the quantization level. - View Dependent Claims (66, 67, 68, 69)
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70. A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method comprising:
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quantizing audio information by a quantization level;
computing a first quality measure indicating quality of the audio information as quantized by the quantization level;
comparing the first quality measure to a second quality measure for the audio information, the second quality measure indicating quality of the audio information as quantized by a previous quantization level; and
if the comparing indicates non-monotonicity of quality measure as a function of quantization level, designating the quantization level as inferior. - View Dependent Claims (71, 72)
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73. In an audio encoder, a computer-implemented method comprising:
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determining a first bit count associated with a first quantization level;
determining a second bit count associated with a second quantization level;
determining a third quantization level within a quantization level range based upon location of a target bitrate on a trajectory of bit count as a function of quantization level, wherein the first and second quantization levels define endpoints of the quantization level range, wherein the first and second bit counts define endpoints of the trajectory, and wherein the function relates bit count in proportion to inverse logarithm of quantization level.
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74. In an audio encoder, a computer-implemented method comprising:
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determining a first quality measure associated with a first quantization level;
determining a second quality measure associated with a second quantization level;
determining a third quantization level within a quantization level range based upon location of a target quality on a trajectory of quality measure as a function of quantization level, wherein the first and second quantization levels define endpoints of the quantization level range, wherein the first and second quality measures define endpoints of the trajectory, and wherein the function relates logarithm of quality measure in proportion to inverse logarithm of quantization level.
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75. In an audio encoder, a computer-implemented method comprising:
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in a quality control quantization loop iteration, selecting a first uniform, scalar quantization step size using a first set of rules and quantizing audio information using the first uniform, scalar quantization step size; and
in a bit-count control quantization loop iteration, selecting a second uniform, scalar quantization step size using a second set of rules and quantizing the audio information using the second uniform, scalar quantization step size, wherein the second set of rules is different than the first set of rules.
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76. A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method comprising:
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computing a value of a control parameter for a block of audio information; and
filtering the value as part of a sequence of previously computed values of the control parameter, wherein the filtered value of the control parameter is for regulating at least in part quantization of the block of audio information. - View Dependent Claims (77, 78, 79, 80, 81, 82, 83)
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84. An audio encoder comprising:
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means for computing a value of a control parameter for audio information;
a filter for lowpass filtering the value as part of a sequence of previously computed values for the control parameter; and
a quantizer for quantizing the audio information, wherein the filtered value of the control parameter at least in part regulates the quantizer. - View Dependent Claims (85, 86, 87, 88, 89, 90)
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91. A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method comprising:
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comparing a desired buffer fullness level to a current buffer fullness level;
correcting bias in a model by adjusting a value of a control parameter for a block of audio information based at least in part upon a result of the comparing, wherein the adjusted value of the control parameter is for regulating at least in part quantization of a subsequent block of audio information. - View Dependent Claims (92, 93, 94, 95)
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96. An audio encoder comprising:
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a virtual buffer for storing bits for one or more blocks of frequency coefficients, the virtual buffer having a current fullness level and a desired fullness level; and
means for correcting model bias by adjusting a value of a control parameter based at least in part upon a result of comparing the desired fullness level to the current fullness level, wherein the adjusted value is for regulating at least in part subsequent quantization. - View Dependent Claims (97, 98, 99, 100)
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Specification